Time is a concept of the physical body, a product of our mind and senses.
It is perspective granted by the degradation of the flesh and the passing of the seasons. In essence the energy that makes up reality Cannot be destroyed, only changed. Therefor, regardless of how much "time" passes the fundamentals of existance are the same.
Intense meditation can allow one to spiritually view past events, present events and occasionally future events. We cannot travel to effect the events because its mathmaticly impossible. Magic doesn't shatter the rules of nature, it simply exists within the higher "hidden" scale of rules that most have yet to acknowledge.